Electron beam centering device for cathode-ray tubes



Feb. 26, 1952 R HEPPNER 2,586,948

ELECTRON BEAM CENTERING DEVICEFOR CATHODE-RAY TUBES' Filed March 22, 1951 Patented Feb. 26,

UNITED STATES PATENT OFFICE CATHO D E-RAY TUBE Myron=R-.'-Heppner, Round Lake, 111. Applicatiiin March 22, 1951, serial No. "216,961

(sllai'ins. 1

This invention relates to nnprcveinentsma magnetic centering device for television pictures projected upon the fluorescent screen of a "television or cathode ray tube, and refers particularly to a device which is simple and economical in construction and can be conveniently and simply operated to effectively orient or center the electron beam of the tube.

Manufacturing limitations prohibit a perfect alignment of the electron gun and other physical elements of a cathode ray tube with. the center of the fluorescent screen. Expedients have heretofore been proposed for centering the electron beam, but such expedients have been impermanent and require periodic adjustments and replacement and in some cases the device for centering the beam altered the focus thereof requiring the simultaneous adjustment of a number of variables.

My present invention contemplates 'a magnetic centering device employing permanent magnets of aluminum-nickel-iron-cobalt type, commercially known as Alnico, the device being so constructed that relatively small permanent magnets may each establish a component magnetic field of desired intensity and shape, which by proper manipulation of the magnet-carrying devices, may form a resultant field adaptable for acting on the electron beam to properly orient the beam with respect to the fluorescent "screen of the cathode ray tube.

Briefly described my beam-centering or orienting device comprises a pair of ferro magnetic discs, each having a substantially circular periphery and each being provided with an eccentrically positioned substantially circular aperture. The discs are so associated with each other as to have their respective central apertures concentric, the discs being in plane 'parallel relationship with each other and being relatively rotatable about the center of the central apertures. Each disc carries "a relatively small permanent magnet with its poles disposed on a line spaced from and substantially parallel to a tangent to the defining edge of the internal aperture of the disc. By relatively rotating the discs the magnetic direction of the held within said apertures may be shifted with respect to the center of said apertures. The device is. adapted to embrace the neck of a cathode ray tube with the axis of the tube substantially coincident with the centers of the disc apertures. Hence, manipulation of the discs exerts transverse magnetic forces upon the electron beam which travels along substantially the axis of the tube neck.

"Other objects and advantages of my invention will be 'ap'paren't from the accompanying drawing and following detailed description.

In the drawing, Fig. 1 is a side elevational view of a conventional cathode ray tube with an "embodiment of the present invention mounted onthe neck of the tube.

Fig. 2 is an enlarged front elevational view of the centering device comprising the concepts of the present invention.

Fig. 3 is a sectional view taken on line 33 of Fig. 2.

Fig. 4 is an enlarged detailed sectional view of one of the permanent magnets mounted upon thedevic'e.

Fig. 5 is 'a sectional view taken on line 5-5 of s Fig. 4.

Fig.5 is a fragmentary detailed perspective view of the magnet-clamping lugs upon one oi the rings.

Fig. '7 is a fragmentary detailed perspective view of the magnet-clamping lugs upon one of the ring-shifting arms.

Fig. 8-is a diagrammatic view of the magnetic field established within the centering device with the magnets spaced degrees apart.

Fig. 9 is a similar view with the magnets in quadrature.

Referring in detail to the drawing, I indicates a conventional cathode ray tube of the type employed in television sets, the tube being shown diagrammatically. The tube carries a base 2 from which a plurality of connecting prongs 3 project whereby the elements of the tube may be suitably connected to an external circuit. The tube I also comprises a neck portion 4 which flares outwardly as indicated at 5, the outermost flared portion thereof terminating in a face 6, the rear surface of which is provided with a fluorescent coating of such nature that impingement of an electron beam thereupon causes the fluorescent material to give ofi light. Upon the neck of the tube a conventional ion trap i may be positioned and scanning coils 8 of conventional construction may also embrace the tube neck. A centering device 9, which comprises the subject matter of the present invention is mounted upon the neck ofthe tube in substantially the position shown relative to the ion trap and the scanning coils.

The function of the centering device 9 is to so orient or position the electron beam given off by the electron gun IE3 that the beam, when the tube is normally inactive, will impinge upon the geometrical center of the fluorescent screen.

The device 9 comprises a cylindrical collar H Which may be constructed of fiber, hard rubber, aluminum or other non-magnetic material. A pair of non-magnetic spring members I2 may be riveted upon diametrically opposite sides of the inner portion of the cylindrical collar II, the spring members l2 preferably being constructed of phosphor-bronze, When the device 9 is mounted upon the neck 4 of the cathode ray tube I the cylindrical collar II embraces said neck and is substantially coaxial with. said neck, the collar being retained in a predetermined position upon the neck 4 by means of the spring arms I2 which frictionally engage the outer walls of the tube neck. In this fashion the device 9 occupies what may be referred to as a semi-permanent position upon the neck 4.

A pair of ferro-magnetic discs I3 and I4, each being provided with a circular aperture, snugly embrace the periphery of the cylindrical collar II, said apertures being respectively eccentric with respect to the peripheries of each of the discs I3 and I4. Spring fingers I are mounted upon the outer surface of the cylindrical member II, said spring fingers being disposed diametrically opposite each other and having their arms adapted to bear upon the face of the ferro-magnetic disc l4. The spring fingers I5 are constructed of a non-metallic material such as phosphor-bronze. The cylindrical collar II at one of its ends is provided with an annular outwardly extending ledge I6, the arrangement being such that the ferro-magnetic disc I3 is positioned adjacent said ledge. Accordingly, the spring fingers I5 which resiliently bear upon the surface of the ferro-magnetic disc I4 tend to urge the discs I3 and I4 together into magnetic contact with each other and tend to urge both discs toward the annular ledge IS. The arrangement is such that the discs I3 and I4 may be rotated relative to the collar II and relative to each other, said discs during the rotating operation being urged toward each other by means of the spring fingers I5 whereby said discs may be positioned in a semi-permanent fashion with respect to each other.- By semi-permanent is meant that the discs can be readily moved when an external force is applied but will not readily move relative to each other or relative to the collar II unless such external force is applied.

By virture of the eccentrically located central apertures in the discs I3 and I4 it will be noted that the radial width of the discs decrease from a maximum to a minimum throughout 180. At that portion of each of the discs where the width of the discs is a maximum said discs are each recessed, as indicated at I! in Fig. 6 and are provided with opposite struck up lugs I8. As will be hereinafter more fully described the lugs III are adapted to provide confining walls for rectangular sectioned permanent magnets. The lugs I8 upon the disc I3 extend outwardly from the surface of the disc I3, said lugs extending away from the observer as viewed in Fig. 2. Conversely, the lugs I8 carried by the disc I4 extend in the opposite direction relative to the disc I4, that is, said lugs extend toward the observer as viewed in Fig. 2. Accordingly, it can readily be seen that magnet A carried by the disc I3 is offset axially with respect to magnet B carried by the disc I4.

In order to provide a convenient means for moving the disc l3 circumferentially upon the collar II and also to assist in securing the magnets A and B upon the discs, handles I9 are employed. The handles I9 are preferably constructed of a non-magnetic metallic material such as aluminum or the like. At one end of each of the handles IS a lug 20 is formed, said lug being disposed at substantially right angles to the plane of the handle proper. Adjacent the lug 20 opposite lugs 2| are formed integral with the handle I9, said lugs being extensions of the sides of the handle. The lugs 2| are also disposed at substantially right angles to the plane of the handle proper and are disposed at substantially right angles to the lug 20, In substantial alignment with the upper edges of the lugs 2|, as viewed in Fig. 7, a tongue 22 is struck up from the material of the handle I9.

The arrangement is such that the space defined by the lugs 2|, lug 20 and tongue 22 is adapted to be occupied by the permanent magnets, said lugs cooperating with the struck up lugs I8 of the rings or discs I3 and I4.

At the base of each of the lugs I8 an aperture 23 is provided and at the outer edges of each of the lugs 2I tongues 24 are carried. When the various lugs are associated together to confine the magnets A and B the tongues 24 are adapted to extend through the apertures 23 and said tongues are bent toward each other as shown best at 25 in Fig. 2.

In this fashion the magnets A and B are securely mounted upon the respective discs I3 and I4, said magnets making snug magnetic contact with the lugs l8. In addition, the handles I9 are simultaneously secured in substantially rigid relationship to the discs I3 and I4 whereby said discs may be conveniently rotated with respect to the collar II and with respect to each other.

In positioning the magnets A and B upon the discs I3 and I4 respectively, the magnets are so disposed as to have their opposite poles in contact with the oppositely disposed lugs I8. Hence, as viewed in Fig. 2, the respective north and south poles of the magnet A are indicated by the letters N and S respectively and the north and south poles of the magnet B are indicated by the letters N and S respectively. It will be noted that in the position shown in Fig. 2 the north pole of magnet A is directly opposite the north pole of magnet B along a line parallel to the diameter and the south poles of the respective magnets are disposed in a similar relationship to each other.

In utilizing the device 9, the device is positioned upon the neck 4 of cathode ray tube I as indicated in Fig. 1 and as will be hereinafter more fully described if the electron beam does not normally impinge upon the geometrical center of the screen of the tube the discs I3 and I4 may be rotated relative to the collar II and relative to each other, the rotation of the discs being conveniently accomplished by means of the respective handles I9. It can readily be seen that when the discs I3 and I4 are rotated relative to each other, the magnets A and B occupy different angular relationships with respect to the axis of the cathode ray tube and with respect to each other. As will be hereinafter more fully described, each magnet A and B establishes a component magnetic field in the neck 4 of the tube and by changing the angular positions of the magnets with respect to the axis of the tube neck and with respect to each other, the resultant field adjacent the axis of the tube neck will be changed thereby exerting a radial magnetic force upon the electron beam which may tend to radially shift said beam.

Referring particularly to Fig. 8, for purposes of explanation and for purposes of establishing a reference point or datum condition, it is asa counterclockwise direction, that is, to-three oclock position, as shown in Fig. 9. The resultant field will then have a'direction. from the third quadrant alon substantially a45 angle to the first quadrant, as shown in Fig. 9.

Maintaining magnet A and disc [3 stationary and moving disc I4 to position magnet B *in the nine, oclock position. the resultant field will have a directionfrom the second quadrant to the fourth quadrant along substantially a 45 line.

Hence, by maintaining disc 13 stationary, as described, and moving disc M, the angle of the field direction may be changed to substantially all degrees, the field direction being generally from left to right, as viewed from the base end of the tube.

To have the field move from right to left, throughout any desired angle, disc I4 may be maintained stationary and disc 13 may be rotated, magnet B then being in the datum positionoccupied by magnet A, as hereinbefore described.

Of course, the description of the manipulation of the discs I3 and i4 hereinbefore set forth is for illustration only, and said discs and magnets may occupy, as desired, any angular relationship with respect to the tube axis and may occupy any angular relationship with respect to each other, and may be moved angularly relatively to each other in any fashion, that is, simultaneously or separately, in order to secure the desired results of shifting the electron beam to center it with respect'to the tube screen.

It can readily be appreciated that for predetermined settings of the discs and magnets to secure a desired field direction, the field strengths will be-different. That is, for a predetermined field direction, by the proper relative positioning of the discs and magnets, a predetermined field strength may also be secured.

It is possible to dispose magnets A and B in superimposed or aligned relationship, and if the magnets are of equal strength, which is preferably the case, it would appear that the magnets would neutralize each other.

and, hence, a weak component field will be established. In some cases, this characteristic of my device may be employed to obtain a desired orientation or centering of the electron beam where the tube components are only slightly imperfect.

Although the device comprising my invention may be employed upon either electrostatically and magnetostatically focus controlled tubes, it finds its greatest suitability to tubes of the first-mentioned type.

I claim as my invention:

1. A centering device for an electron beam in a cathode ray tube which comprises a pair of Termmagnetic discs each having an eccentric aperture, means for mounting said discs in plane-parallel relationship with each other with said apertures in alignment and with said discs rotatable with respect to each other about the centers of said apertures, a permanent magnet carried on each However, I have found that the magnets are seldom precisely identical 6 disc, 'each'magnet being positioned upon that portion of each disc of greatest radial width, and means 'for mounting said discs upon the neck of a cathode ray tube with thelongitudinal axis of said necksub'stantially coincident with the centers of said apertures.

2. A centering device for an electron beam in a cathode ray tube which comprises a pair of ferromagnetic discs each having an eccentric aperture, means for mountin said discs in plane-parallel magnetic contacting relationship with each other with said apertures in alignment and with said discs rotatable with respect to each other about thecenters of said apertures, a'permanent magnet carried on each disc in magnetic contact therewith, each magnet being positioned upon that portion of each disc of greatest radial width, and means for mounting'said discs upon the neck of a cathode ray tube with the longitudinal axis of said neck substantially coincident with the centers of said apertures.

3. A centering device for an electron beam in a cathode ray tube which comprises a pair of similar circular ferro-magnetic discs each having a similar eccentric circular aperture, means for mounting said discs in plane-parallel magnetic contacting relationship with each other with said apertures in alignment and with said discs rotatable with respect to each other about the centers of said apertures, a permanent magnet carried on each disc in magnetic contact therewith, each magnet being positioned upon that portion of each disc of greatest radial width, and means for mounting said discs upon the neck of a cathode ray tube with the longitudinal axis of said neck substantially'coincident with the centers of said apertures.

4. A centering'device for an electron beam in a cathode ray tube which comprises a pair of similar circular ferro-magnetic discs each having a similar eccentric circular aperture, means for mounting said discs in plane-parallel magnetic contacting relationship with each other with said apertures in alignment and with said discs rotatable with respect to each other about the centers of said apertures, a permanent magnet carried on each disc in magnetic contact therewith, each magnet being positioned upon that portion of each disc of greatest radial width, a line connecting the north and south poles of each of said magnets being parallel to the tangent to the defining edge of the respective disc aperture at the point of greatest width of the disc, and means for mounting said discs upon the neck of a, cathode ray tube with the longitudinal axis of said neck substantially coincident with the centers of said apertures.

5. A centering device for an electron beam in a cathode ray tube which comprises, a tubular non-magnetic collar, a similar pair of circular ferro-magnetic discs each having a circular eccentric aperture, means for mounting said discs in relatively rotatable plane-parallel relationship upon said collar, a permanent magnet carried on each disc in magnetic contact with said disc, each magnet being positioned upon that portion of each disc of greatest radial width, and means for mounting said collar in embracing relationship upon the neck of a cathode ray tube.

6. A centering device for an electron beam in a cathode ray tube which comprises, a tubular non-magnetic collar, a similar pair of circular ferro-magnetic discs each having a circular eccentric aperture, means for mounting said discs in relatively rotatable plane parallel relationship upon said collar, a permanent magnet carried on each disc in magnetic contact with said disc, each magnet being positioned upon that portion of each disc of greatest radial width, a line connecting the north and south poles of each of said magnets being parallel to the tangent to the defining edge of the respective disc aperture at the point of greatest radial width of said disc, and means for mounting said collar in embracing relationship upon the neck of a cathode ray tube.

7. A centering device for an electron beam in a cathode ray tube which comprises, a tubular nonmagnetic collar, a similar pair of circular ferromagnetic discs each having a circular eccentric aperture, means for mounting said discs in relatively rotatable plane-parallel relationship upon said collar, a permanent magnet carried on each disc in magnetic contact with said disc, the magnets being carried in similar positions upon said discs and similar faces of said discs being in contact with each other whereby said magnets are offset with respect to each other relative to the plane of contact of said discs, each magnet being posit oned upon that portion of each disc of greatest radial width, a line connecting the north and south poles of each of said magnets being parallel to the tangent to the defining edge of the respective disc aperture at the point of greatest radial width of said disc, and means for mounting said collar in embracing relationship upon the neck of a cathode ray tube.

8. A centering device for an electron beam in a cathode ray tube which comprises a similar pair of circular ferro-magnetic discs each havingasimilar circular eccentric aperture, means for mounting said discs in relatively rotatable plane-parallel magnetic contacting relationship with each other with said respective apertures in alignment, a permanent magnet carried on each disc in magnetic contact therewith, each magnet being positioned upon that portion of each disc of greatest radial width, a line connecting the north and south poles of each of said magnets being parallel to the tangent to the defining edge of the respective disc aperture at the point of greatest radial width of said disc, said magnets when the discs are in contact with each other being oppositely offset from said plane of contact, like poles of said magnets when said magnets are diametrically opposite each other being opposite to each other, and means for mounting said discs upon the neck of a cathode ray tube with the longitudinal axis of said neck substantially coincident with the centers of said apertures.

9. A centering device for an electron beam in a cathode ray tube which comprises, a non-magnetic tubular collar, a pair of ferro-magnetic discs each having eccentric apertures, means for mounting said discs in relatively rotatable planeparallel and frictional contacting relationship with each other upon said collar, said means comprising an annular ridge carried by said collar against which one of said discs abuts and resilient members carried by said collar which resiliently bear upon the other disc to urge said discs together and toward said ridge, a permanent magnet carried on each disc in magnetic contact therewith, each magnet being positioned upon that portion of each disc of greatest radial width, and means for mounting said collar upon the neck of a cathode ray tube.

10. A centering device for an electron beam in a cathode ray tube which comprises a similar pair of circular ferro-magnetic magnetized discs each having a similar eccentric circular aperture, means for mounting said discs in relatively rotatable plane-parallel magnetic contacting relationship with each other with said apertures in alignment, and means for mounting said disc upon the neck of a cathode ray tube with the longitudinal axis of said neck substantially coincident with the centers of said apertures whereby relative rotation of said discs changes the magnetic field within said tube neck.

MYRON R. HEPPNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,428,780 Bowen Oct. 14, 1947 2,533,688 Quam Dec. 12, 1950 2,533,689 Quam Dec. 12, 1950 2,544,898 Obszarny et a1 Mar. 13, 1951 

